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Instruction handbook Mains filters BFN
Document No.: 5.09010.03
3TECHNICAL DATA
3.1 Operating conditions
3.1.1 System types
There is a differential structure of current supply systems and it is distinguished between
three basic types, referring to their grounding, which is accordant to DIN VDE0100 part
300 and accordingly to IEC 60364:
m In a TN-system one point is directly grounded
(signal ground). The cabinet of the elec-
trical installation is connected via protective
conductors and accordingly PE-conduc-
tors with this point.
m In a TT-system a point is directly grounded (
signal ground). The cabinet of the electric
installation is connected to ground connections, which, however, are separated from
the signal ground.
m In an IT-system there is no direct connection between activ
e conductors (L1, L2, L3,
N) and grounded parts (PE). The cabinets of the electrical installation are grounded.
The separation is reached, by the use of an isolating transformer or with the use of an
independent current source (generator, battery).
If there is an adequate low-impedance grounding within the TN- or the TT-system, then
a line-side fuse is activated. A high-impedance grounding does not activate the fuse, so
that the ground currents (error current) can be potentially dangerous. For this reason, cir-
cuit breakers are used for the error current monitoring.
At a short-circuit to ground, no ground current can flow and the line-side fuses cannot be
activated, by which the operation can be kept up. Only a second short-circuit to ground at
another phase would cause an current error, which can trigger a fuse. In order to detect
the first short-circuit to ground an insulation monitor and for the second short-circuit to
ground, a current error monitoring, are necessary.
Supported system types
NOTICE!
T
he operation of the mains filters BFN is possible with IT- and TN/TT-systems.
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